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(−)-Patagonic acid (1) is a clerodane diterpene isolated from several plants from the Alismataceae, Asteraceae, Euphorbiaceae, Fabaceae, Lamiaceae, Salicaceae, Sapindaceae, and Velloziaceae families, and its biological potential as an inhibitor of butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) and as an anti-inflammatory compound has been described. Furthermore, the enantiomer (+)-1 is also described in Fabaceae and Verbenaceae. A lack of formal studies about the absolute configuration (AC) determination of 1 is emphasized. Thus, the present manuscript describes the AC determination of patagonic acid (1). The chemical correlation of (−)-1 from (−)-hardwickiic acid (2) was achieved by a simplistic oxidative process. The specific rotation value and electronic circular dichroism (ECD) analysis allowed for the AC determination of (−)-1 as (5R,8R,9S,10R)-(−)-patagonic acid. ECD revealed a positive exciton chirality (EC) phenomenon in both (−)-1 and (−)-2, which is directly associated with their configuration and conformational preferences, which were assessed by DFT calculations at the B3LYP/DGDZVP level of theory. Since the NMR data of (+)-1 are fully coincident with those from its enantiomer studied herein, the chirality of (5S,8S,9R,10S)-(+)-patagonic acid could also be determined. These experimental conclusions deeply complement the literature related to clerodane compounds biosynthesized in several families of plants of scientific interest. Full article

In this study, nine neo-clerodane-type diterpenoids (1–9) were isolated from the dichloromethane extract of Salvia guevarae Bedolla & Zamudio leaves. Compounds 1–6 were new natural products, and 7–9 were acetone artifacts. In addition, four neo-clerodanes diterpenoids (10–13) previously described from different sources and six triterpenoids—identified as 3β,20,25-trihydroxylupane, oleanolic acid, 3β-O-acetyl-oleanolic acid, ursolic acid, 3β-O-acetyl-betulinic acid, and 3β,28-O-diacetyl-betulin—were isolated. Additionally, five flavonoids were also isolated from the methanol extract: quercetin-3-O-β-xylopyranosyl-(1 → 2)-β-galactopyranoside, taxifolin-7-O-β-glucopyranoside, naringenin-7-O-β-glucopyranoside, a mixture of 2R and 2S eriodictyol-7-O-β-glucopyranoside, caffeic acid, the methyl ester of rosmarinic acid, and rosmarinic acid. The structure of the isolated compounds was established by spectroscopic means, mainly ¹H and ¹³C NMR, including 1D and 2D homo- and heteronuclear experiments. The absolute configuration of 1 and 10 was ascertained via an X-ray analysis, and that of the other compounds via ECD. The antiproliferative activity of some diterpenoids was determined using the sulforhodamine B method, where guevarain B (2) and 6α-hydroxy-patagonol acetonide (7) showed moderate activity against the K562 line, with IC₅₀ (μM) = 33.1 ± 1.3 and 39.8 ± 1.5, respectively. The NO inhibition in RAW 264.7 macrophage activity was also determined for some compounds, where 2-oxo-patagonal (6), 6α-hydroxy-patagonol acetonide (7), and 7α-acetoxy-ent-clerodan-3,13-dien-18,19:16,15-diolide (10) were proven to be active, with IC₅₀ (μM) of 26.4 ± 0.4, 17.3 ± 0.5, and 13.7 ± 2.0, respectively. The chemotaxonomy of Salvia guevarae is also discussed. Full article